Dental restorations or implant abutments often consist of ceramic materials or of metals which can be adapted to tooth defects in different ways. The restoration is generally inserted into the cavity before securing it in order to check the fit (“try-in”). Even when a rubber dam is used, contamination by protein-containing bodily fluids, such as for instance saliva, dentinal fluid, sulcus fluid, blood, is virtually unavoidable here. The proteins are adsorbed on all clinically common ceramics and metals by strongly ionic to partially covalent interactions. If this is followed by adhesive securing by means of customary adhesion promoters (“primers”) and radically curing fixing cements and composites, such protein contaminations lead to a clear weakening of the bonding effect between restoration material and cement or composite.
The problem of protein pollution is the subject of some scientific publications which also discuss different possible solutions. Yang et al., Dental Materials, 24:508-513 (2008) describe sandblasting with Al2O3 particles in order to remove saliva contaminations.
Y. Aboush, J. Prosth. Dent., 80(6):649 (1998), recommends cleaning porcelain surfaces with phosphoric acid.
Quaas et al., Dental Materials, 23:506-512 (2007), compare air abrasion with Al2O3 particles and treatment with 37% phosphoric acid or with isopropanol in order to remove saliva contaminations. Air abrasion proved to be the most effective for cleaning zirconia ceramic. Yang et al., J. Dent. Res., 86(8):749-753 (2007) come to comparable results.
T. Bock, U. Salz, IAD Conference (2008), Xi'An (CN)) achieved a maximum bonding strength to ZrO2 after cleaning with 2% NaOCl.
However, it was shown that on metal oxides and base metals the phosphoric acid cleaning brings with it a decrease in the bond strength compared with uncontaminated, uncleaned reference samples. Nor can protein adsorbates be completely removed by the hitherto available non-abrasive mechanical methods (e.g. water jet, polishing brushes, ultrasonic bath) before the adhesive securing of restoration materials. Even the combined use of mechanical cleaning methods with the available cleaning agents, such as e.g. detergent solutions and dental polishing pastes, solvents, such as petrol, ethanol or acetone, acids, lyes, oxidizing agents, such as carbamide peroxide, hypochlorite or hydrogen peroxide, or solubilization aids, such as urea, does not lead to an appreciable improvement in the bonding values.
The only method known in the literature for effectively cleaning protein-contaminated dental ceramic and metal surfaces is blasting with abrasive blasting agents (such as e.g. corundum). The surface abrasion occurring with this method removes all of the adsorbed contaminants and thus makes possible a bond comparable to uncontaminated surfaces. However, the disadvantages are the negative influencing of the fit of the restoration by the abrasion, the incompatibility with abrasion-sensitive veneering materials, the unavoidable damage to delicate intersections, the lack of availability of suitable equipment in dental practices and the barely possible intra-oral applicability. Sandblasting is therefore suitable for clinical situations only under certain conditions.